Patent Application
20250087783
The field to which the disclosure generally relates includes methods and assemblies for thermal management of the temperature of battery components and thermal safety features for limiting cell-to-cell thermal propagation within a battery. More particularly, but not exclusively, the invention relates to a battery module having a number of electrically interconnected battery cells, wherein the individual battery cells are temperature-controlled by means of heat removal and heat insulation.
In this application “thermal management” function and objective shall mean maintaining a battery and its individual subassemblies withing desired temperature limits (minimum and maximum) and within a desired variation (ΔT) band from one subassembly to another. “Thermal safety” function shall mean limiting heat propagation between battery subcomponents, in particular from cell to cell, with the objective of preventing a thermal runaway event (defined below).
In the present context, the terms “battery cell”, “battery module”, “battery section”, and “battery pack” (as well as their shortened variants “cell”, “module”, “section”, and “pack”) are used to describe different levels of components of an overall battery assembly. For example, numerous individual battery cells form the building blocks of battery modules. Multiple battery modules (in conjunction with ancillary equipment) in turn make up a battery pack.
For purposes of this application, a cell is the smallest unit of a battery pack that includes a single anode electrical connection and single cathode electrical connection on the exterior or a sealed housing that contains one or more pairs of anode and cathode elements. A cell is a single electrochemical unit, whereas a battery is made up of one or more electrically interconnected cells joined in series, parallel or both, depending on desired output voltage, current or capacity.
A battery apparatus may include one or more battery packs suitably sized to provide electrical power to the vehicle. Battery packs are made up of battery sections which may be made up of numerous battery modules each of which is in turn made up of one or more battery cells that deliver electrical current to a load. The battery cells are electrically interconnected.
Battery packs are made up of sections which may be made up of numerous battery modules each of which is in turn made up of one or more battery cells that deliver electrical current to a load. The number of battery cells within the larger battery module, section, pack or related structure will be appreciated by those skilled in the art to coincide with the power needs of the device receiving electric current from the battery, as well as the thermal operating requirements of the cells within the battery. In such batteries, current flow, both charge and discharge, generates heat inside the cells and in their interconnection systems.
Electric Vehicles (EVs) use lithium-ion batteries comprised of cells. The performance of a lithium-ion battery cell is very dependent on its temperature. When overheated, the cells can experience degraded electrical performance, damage, and reduced lifespan. Thus, lithium-ion batteries require thermal management systems to maintain a constant temperature with very low temperature deviations (the temperature distribution over a cell should be uniform with a maximum deviation of less than 5° C.) so that they can operate efficiently without damages or failures.
Additionally, lithium-ion batteries may experience a failure called thermal runaway. The term thermal runaway event refers to an uncontrolled increase in temperature in a battery system. Thermal runaway is a chain reaction within a battery cell that can be very difficult to stop once it has started. It occurs when the temperature inside a battery reaches the point that causes a chemical reaction to occur inside the battery. This chemical reaction produces even more heat, which drives the temperature higher, causing further chemical reactions that create more heat. During a thermal runaway event, the generation of heat within a battery system or a battery cell exceeds the dissipation of heat, thus leading to a further increase in temperature. A thermal runaway event may be triggered by various conditions, including a short circuit within the cell, improper cell use, physical abuse, manufacturing defects, or exposure of the cell to extreme external temperatures.
One of the important issues in the construction of an electric vehicle is the thermal management and thermal safety systems of the battery (notably lithium-ion batteries have been widely used in electric vehicles).
Thermal management is essential for the performance and operating life of electric vehicle batteries and several studies, disclosures, and patent documents deal with this issue.
U.S. Pat. No. 10,686,171 discloses a battery module comprising a plurality of bells (or mono-batteries) and a plurality of isolating plates, each isolating plate being interpose between two adjacent cells. The isolating plates comprise through holes forming air thermal resistance. The isolating plates are made in a thermosetting resin and the volume of the isolating plates can be expanded when the temperature of one cell exceeds 200 degrees Celsius.
The expansion in case of high temperature can cause damages of the cells. Besides, the thermal propagation between the cells is decreased, but only to a certain extent.
It is also known to use cooling fins to conduct heat away from the battery cells. The cooling fins may be made of a material with a high thermal conductivity (alternatively, low thermal resistance) to transfer heat to a cooler or heat exchanger.
US20110189525 for instance discloses a heat exchanger structure for use in a battery unit and arranged between opposing surfaces of a first and a second battery stack. The heat exchanger defines one or more fluid flow passages and is used to dissipate heat.
It is also known to cool electric vehicle batteries by forced convection with a forced air or liquid coolant circulated through cooling passages. For instance, documents US2021135307A1, US2014308551A1, CN102117945 and US2008305388A1 disclose a liquid-cooled battery system. US2016204483A1 also discloses cooling fins configured to receive the flow of the liquid coolant through a coolant channel and discloses cell-to-cell thermal insulation within a battery system using passive cooling, such as conduction, radiation, or convective cooling without active circulation of a cooling fluid.
In US2008/0305388, thin, substantially planar, but not necessarily flat, heat conducting fins in contact with the individual battery cells conduct heat away from the cells to a heat exchanger comprising pipes containing a cooling fluid. The fins connect to the pipe at an extremity of the fin and the pipe is outside the perimeter of the cell pack.
In US2014/0308551, various embodiments disclose inter-cell thermal fins incorporate coolant fluid conducting channels within the fins between adjacent cells. The fluid conducting channels are in in fluid connection with a manifold outside the perimeter of the cells.
US2021/0135307 also describes various embodiments in which a cooling fluid circulates through fluid channels within a substantially planar cooling fin located between adjacent cells.
In US20160204483, multiple embodiments also describe cooling fins with fluid channels for actively circulated coolant and describe the addition of elements that will allow for passive (for example, gravity) flow of coolant in the event that active (pumped) flow is lost, to mitigate spreading of a thermal runaway between cells.
CN102117945 uses anisotropic heat conduction and discloses a device comprising combined heat conductive plate comprising a heat conductive layer and a thermal insulation layer. The combined heat conductive plate may be arranged between two element cells.
These systems require a complex fabrication and there is still a need to provide cooling system which ensure a thermal management function by removing excess heat from the cells while limiting thermal propagation between the battery cells or the battery modules or between a battery pack and the rest of the vehicle.
JP2020072005A is directed to a heat transfer suppressing sheet for batteries. JP2020072005A discloses an arrangement comprising two flat sheets made of a heat absorbing or insulating material and a corrugated sheet extending between the two flat sheets. The corrugated sheet has the same heat absorption and/or heat insulation performance as the flat sheet 20. The heat will be absorbed in order to use for evaporating water or any material.
The materials of the different layers (flat sheets and corrugated sheet) are very specifics. The heat transfer suppressing sheet is particularly expensive and difficult to manufacture.
The present invention relates generally to a thermal fin to enable cooling of individual battery cells, battery modules, or battery packs and to insulate between adjacent battery cells, battery modules, or battery packs. The present invention also relates to a battery module comprising such thermal isolators.
An aspect of the invention will involve the choice of certain material and their arrangement to achieve the thermal management and thermal safety functions. Thermal Interface Materials (TIMs) are useful for thermal management in electronic components, as they enhance heat transfer from a heat-generating component (here, a battery cell) to a heat dissipater (heat sink, heat exchanger, or cooler). One important aspect when selecting a TIM for a certain application is knowing the material's ability to transfer heat, which is often given by way of thermal conductivity and/or thermal resistance. Thermal conductivity is a material property and describes the ability of the given material to conduct heat. A material with high thermal conductivity is a better thermal conductor. This property is independent of material size, shape, or orientation in a homogeneous material, and because of this, thermal conductivity is an idealized value. Thermal conductivity is measured in units of Watts/meter-Kelvin.
Thermal resistance is merely the mathematical inverse of conductivity. Since both thermal conductivity and resistance are a function of distance (note “meter” in the denominator of Watts/meter-Kelvin), thinner TIMs transfer heat more efficiently than thicker ones. The thermal resistance of a structure is measured between a first point and a second point and depends on the thermal resistance of the individual homogenous elements and all contact resistances in between. When a structures' thermal resistance is lower, the structure is a better thermal conductor. Factors such as surface roughness, surface flatness, clamping pressure, presence of adhesive, non-homogeneous, and material thickness all have large impacts on the material's thermal resistance. Thus, thermal resistance accounts for more variables specific to the structure. Thermal resistance is usually expressed in units of m2 K/Watt.
It is an object of the present invention to provide a thermal fin and a battery module that improves the thermal management function by conducting away the heat generated in battery cells to a cooler, for example, and minimizes thermal propagation from cell to cell, module to module and from pack to vehicle. The thermal fin is designed to be arranged between any battery pack-subassembly, such as battery modules, battery cells or battery packs, as disclosed below.
Accordingly, the present invention provides a thermal fin according to claim 1 and a battery apparatus according to claim 11.
More particularly, the thermal fin for a battery apparatus configured to prevent cell-to-cell, module to module and/or pack to vehicle thermal propagation comprises: a first and a second contact unit. The first contact unit (of high thermal conductivity) is in facing contact with a first battery pack subassembly. Such a subassembly being, for example, an individual battery cell, or battery module comprising multiple cells, or a battery pack comprising multiple battery modules. And a second contact unit may be in facing contact with a second battery pack subassembly. A supporting unit (or insulator) is arranged adjacent to the first contact unit. It can also be sandwiched between the first and the second contact unit to create a thermally insulating space between the first and second contact units. The thermal fin extends in a plane and defines a height, and a width, and a thickness. The thermal resistance within the plane is lower than the thermal resistance in a direction normal to the plane, that is across the thickness of the fin, such that the fin provides a thermal management function and a thermal safety function of the battery apparatus. The supporting unit comprises a structure arranged such that an insulating gap (notably a fluid gap, preferably an air gap) is maintained between the first and the second contact unit. The gap forms an insulation layer which prevents the heat transmission between the cells.
The gaps are defined or pre-determined and their designs can be adapted to the shape, size or performance requirements of the battery subassemblies.
Such a sandwiched structure provides a low thermal resistance in the plane of the fin, but a good thermal resistance in a direction normal to the fin plane (across the thickness of the fin). The sandwiched structure allows cooling of individual cells while insulting one cell from an adjacent cell. Thus, less than 20% (and even more particularly less than 10%, and even more particularly less than 5%) of the heat is transferred from one battery pack subassembly to another battery pack subassembly. This arrangement also promotes a uniform temperature within a cell.
In another embodiment, the structure comprises a supporting plate sandwiched between a first and a second spacer, such that insulating gaps, notably fluid gaps, are provided on both sides of the plate. For instance, the plate extends parallel to the first and/or second contact unit. Fluid gaps on both sides of the supporting plate increase the thermal resistance.
In another embodiment, the insulating gap is (are) a fluid gap(s) or more particularly an air gap(s). Such air gap(s) is (are) easy to implement and is satisfactory.
In a still further embodiment, the first and/or second contact unit (conductors) and the structure are made of two different materials. More particularly the first and/or second contact unit are made of a material with high thermal conductivity and the structure or supporting unit is made of materials with a low thermal conductivity. For instance, a high thermal conductivity material is a material having a thermal conductivity in the range of 100 to 3000 W·m-1·K-1. Graphite or copper are materials having a high thermal conductivity. In contrast, a low thermal conductivity material is a material having a thermal conductivity below 400 W·m-1·K-1. Some metal, plastics, or glass have a low thermal conductivity.
In another embodiment, the first and/or second contact unit may be made of copper and/or aluminium with or without graphite. In particular, the first and/or second contact unit is made of copper or is made of copper glued to graphite or is made of aluminium glued to graphite. The first and/or second contact unit may also be made of steel alloy glued to graphite.
In an embodiment, the structure is made of paper. A paper insulator is not expensive and is strong enough for this purpose.
In an embodiment, the structure made of paper can be coupled to contact units made of graphite. Indeed, the graphite offers a good flexibility.
In an embodiment, the structure is made of a mica-based material.
In an embodiment, the thickness of the fluid gap in cross section is of about 0.05 to 1 mm.
In an embodiment, the support structure has a grid pattern. The grid pattern allows a regular thickness of the fluid gap.
In an embodiment, the structure is at least partially corrugated.
In an embodiment, the structure comprises at least one intermediate plate having a first surface and a second surface opposite the first surface, a first plurality of spacers extending from the first surface and a second plurality of spacers extending from the second surface
In an embodiment, the thermal fin has a total thickness in a direction normal to the fin plane of less than 10 mm, and in particular between 0.5 and 2 mm.
The present invention is also directed to a battery module comprising a plurality of electrically interconnected battery cells and a plurality of thermal fins as previously described, wherein each thermal fin is arranged in thermal communication with at least two of said plurality of battery cells or battery pack subassemblies, and wherein the first and the second contact units are connected to a cooler.
In an embodiment, the thermal fins and the plurality of battery cells comprise a substantially planar construction such that an adjacently-facing relation is formed between one thermal fin and at least two of said plurality of battery cells.
In an embodiment, a first thermal fin comprises a first contact unit contacting a first battery cell, a second thermal fin comprises a second first contact unit contacting a second battery cell and a swelling compensator is arranged between two thermal fins.
In an embodiment, the first contact unit is in facing contact with a first battery cell and the second contact unit is in facing contact with a second battery cell.
The invention is also directed to a supporting unit for a thermal fin comprising a structure arranged to establish an insulating gap, wherein the structure comprises at least one intermediate plate having a first surface and a second surface opposite the first surface, a first plurality of spacers extending from the first surface and a second plurality of spacers extending from the second surface.
The invention and its advantages will be better understood from the reading of the following description, given by way of example only and with reference to the accompanying drawings, of which:
The embodiments of the disclosure will be best understood by reference to the drawings, wherein the same reference signs designate identical or similar elements. It will be readily understood that the components of the disclosed embodiments, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the systems and methods of the disclosure is not intended to limit the scope of the disclosure, as claimed, but is merely representative of possible embodiments of the disclosure. In addition, the steps of a method do not necessarily need to be executed in any specific order, or even sequentially, nor need the steps be executed only once, unless otherwise specified.
In some cases, well-known features, structures, or operations are not shown or described in detail. Furthermore, the described features, structures, or operations may be combined in any suitable manner in one or more embodiments. It will also be readily understood that the components of the embodiments, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations.
As previously mentioned, the cooling fins 14 of
As illustrated in
As depicted in
The second contact unit 30 is sensibly identical to the first contact unit 28 (and is arranged in a mirror geometry). The second contact unit 30 comprises a first portion 34 adapted to contact a second battery cell 37 and a second portion 38 adapted to contact the cooler 40. The second portion 38 extends for instance perpendicular to the first portion 34. The second contact unit 30 may be sensibly L-shaped. The second portion 38 has a smaller length and a smaller surface than the first portion. The first portion 34 is substantially planar with a first surface 42 adapted to face outward and contact the second battery cell 37 and a second surface 44 opposite the first surface 42 and inward facing. The first portion 34 for instance has a high of about 100 to 300 mm and a thickness of about 0.05 to 1 mm.
The first and the second contact units 28, 30 are both realized in material having a high thermal conductivity. For instance, the first or second contact unit 30, 28 may be made of graphite, or copper, or aluminium alloy, or steel alloy, or some combination of those materials. More particularly, the contact units 28, 30 are made of copper or graphite. They allow a transport of the heat from the first portion 34 to the cooler 40 thus removing heat from within a battery module. Thus, the thermal conductivity within the fin plane formed by the first portions 34 is relatively high. The contact units transfer heat but do not absorb heat.
Between the first and the second contact units 28, 30 is arranged a supporting unit 32. The supporting unit 32 extends between the second surfaces of the first and the second contact units 28, 30. The supporting unit 32 comprises at least one material different than the material of the first or second contact units 28, 30. The supporting unit 32 may be made of a material or materials having a low thermal conductivity. In any case, the supporting unit 32, in its entirety, as a structure, has a high thermal resistance. For example, the supporting unit 32 could comprise a structure 50 made of metal, plastic, glass, paper, an aluminium, mica or a steel alloy. More particularly, the supporting structure is made of mica or paper material. The mica and paper are lightweight material and allow a low thermal conductivity. More particularly, with these materials a thermal conductivity of about 0.001 W/mK can be achieved. The shape or arrangement of the structure 50 is such that the supporting unit 32 has a thermal resistance higher than the thermal resistance of the contact unit 28, 30. The supporting unit 32 may comprise for instance a structure arranged to provide a fluid gap 52, for instance an air gap, between the first and second contact units 28, 30. Generally, the supporting unit 32 may consist of the structure 50 and the air gap(s) 52.
The first and second contact units 28, 30 generally extend over and contact the majority of the facing surface of a battery cell 36, 37 and are designed to contact the cooler 40. Generally, the supporting unit 32 is not designed to contact the cooler 40, but is designed to entirely extend between, spatially separate, and thermally insulate the first and second contact units 28, 30. The supporting unit 32 forms a thermal barrier.
The thermal fin 26 comprising the supporting unit 32 and the first and second contact units 28, 30 extends in a fin plane, has a fin length Lfin, a fin height Hfin, and a fin thickness tfin. The ratio between the thermal fin height Hfin and the thermal fin thickness tfin is between 25 and 1000. The structure of the thermal fin 26 is sensibly planar and may be flat or shaped to conform to the outer form of the battery cell 36, 37. The thermal resistance within the fin plane is lower than the thermal resistance in a direction normal to the fin plane (across the thickness) due to the insulating fluid gap created by the supporting unit and/or the differing thermal conductivities of the different material used on the contact units 28, 30 versus the supporting unit 32. So constructed, the thermal fin 26 provides the thermal management function of removing heat to a cooler 16, 40 and the thermal safety function of insulating against heat propagation between adjacent cells 26, 37 in a battery module or adjacent battery pack subassemblies.
The supporting unit 32 may have different designs or arrangements, as represented for instance in
In
In
As depicted in
In
In
The structure 50 of
In
In
In
As visible in
In an embodiment, shown in
In
The plate 501 has a thickness tp of about 0.02 to 1 mm. The plate 501 is for instance made of aluminium alloy or steel alloy or paper. As mentioned above, the plate 501 may or may not contact the cooler 40, depending on the plate material thermal conductivity. The dimension (length Lp and height Hp) of the plate 501 are sensibly identical to the dimensions of the first portion 34 of the contact unit 28, 30.
Each grid has a thickness tgrid of about 0.02 to 1.0 mm which allows air gaps 52 of about the same thickness. The grids 64, 66 may be glued to the plate 501 or to the contact units 28, 30.
The thermal fin 26 thus formed by the contact units 28, 30, the grids 64, 66 and the plate 501 has a total fin thickness tfin in a cross-section which is in the range of 0.5 to 10 mm, and more particularly in the range of 0.5 to 4 mm. For instance a thermal fin between battery modules will have a greater thickness than a between-cell thermal fin. Therefore, the first range may apply to a thermal fin between battery modules, wherein the second range applies to a thermal fin between battery cells. In particular a thickness between 0.5 and 2 mm may be provided for a between-cell thermal fin.
A battery subassembly, and for instance a battery module may also be surrounded by one or a plurality of thermal fins as described below, wherein the first contact unit is for instance in facing contact with one battery module, wherein the second contact unit is in contact surface with another battery module.
For illustration purpose,
As seen on the figures, one thermal fin 26 may surround the cell (notably for cylindrical cells or for prismatic cells having an oval cross section) or several thermal fins 26 may be arranged adjacent to each other to surround for instance a battery module.
As defined above, the thermal fin 26 may comprise only one contact unit 28, which constitutes a first contact unit and a supporting structure. Between two thermal fins of such design, a swelling compensator 72 may be arranged, as depicted in
The swelling compensator may be entirely made of a plastic material and comprise a flat body and a plurality of ribs projecting from the flat body toward the first and/or second battery cell. In another embodiment, the swelling compensator 72 may be made at least partially of metal with a spring carrier.
The entire arrangement of the thermal fin allows a high thermal resistance (low thermal conductivity) in a horizontal direction (between two adjacent cells 36, 37 or two adjacent battery subassemblies) and a low thermal resistance (high thermal conductivity) along the length and width of the contact units 28, 30 for heat conduction to the cooler 40. The cooling system comprising a plurality of thermal fins 26 is thus entirely passive, light and not cumbersome.
Although specific examples have been illustrated and described herein, a variety of alternate and/or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific examples discussed herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22176073.9 | May 2022 | EP | regional |
This application is a continuation of PCT Application No. PCT/EP2023/064419, filed May 30, 2023, which claims priority from European Patent Application No. 22176073.9, filed May 30, 2022, the disclosures of which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2023/064419 | May 2023 | WO |
| Child | 18958520 | US |
